1. Field of the Invention
The present invention generally relates to a light-emitting diode and, more particularly, to a light-emitting diode with enhanced light-emitting efficiency, in which the active current is blocked to prevent from entering the region under the top electrode so that the light-emitting efficiency as well as the brightness can be improved.
2. Description of the Prior Art
The light-emitting diode (to be abbreviated as LED hereinafter) has received considerable attention for its advantages such as long lifetime, small size, low heat generation, low power consumption, high response speed, monochromic lighting ability, etc. and has been widely used in applications such as computer peripherals, clock displays, display panels, and many other 3C (computer, communication and consumer) products since the 1960s. Therefore, the LED has become one of the most important light sources.
To further improve the brightness as well as the light-emitting efficiency of an LED, there have been disclosed lots of new techniques such as U.S. Pat. No. 5,153,889 entitled xe2x80x9cSemiconductor light-emitting devicexe2x80x9d filed by Kabushiki Kaisha (Toshiba, JP), U.S. Pat. No. 6,319,778 entitled xe2x80x9cMethod of making light-emitting diodexe2x80x9d filed by Tzer-Perng Chen et al. (United Epitaxy Company, Inc., TW), Taiwan Patent No. 232753 entitled xe2x80x9cMethod for manufacturing light-emitting diode with enhanced brightnessxe2x80x9d filed by ITRI (TW) and Taiwan Patent No. 264573 entitled xe2x80x9cLight-emitting diode with current blocking layerxe2x80x9d filed by Tzer-Perng Chen (TW). These disclosures have significantly improved the LED structure.
FIG. 1 is a cross-sectional view showing a structure of a light-emitting diode according to U.S. Pat. No. 5,153,889. The light-emitting device comprises: a first electrode 17; a substrate 11; an epitaxial LED layer 13 composed of at least a top limiting layer, a light-emitting active layer and a bottom limiting layer to form a p-n junction; a transparent window layer 15; a second electrode 19; and a current blocking layer 14; wherein the current blocking layer 14 is used to reduce the density of the active current flowing through the bottom region of the second electrode 19, so as to relatively increase the density of the active current flowing through the epitaxial LED layer 13 uncovered by the second electrode 19, thereby improving the light-emitting efficiency, as indicated by the arrow d showing the emitted light.
However, for the formation of the current blocking layer 14, the transparent window layer 15 becomes indispensable, which may add complexity to the manufacturing procedure. Moreover, a considerable amount of active current still flows through the second electrode 19 and the bottom region of the current blocking layer 14, as indicated by the dotted line a showing the current path. The light thus generated at the p-n junction emits upward and is absorbed by the current blocking layer 14, as indicated by the arrow b. Therefore, the light-emitting efficiency of the LED is reduced. In addition to the upward emitted light d, slanted light beams such as c1, c2, are also generated at the p-n junction. However, some of the light beams c1, c2 are also blocked and absorbed either by the current blocking layer 14 or the second electrode 19. This also reduces the light-emitting efficiency of the LED.
Therefore, there is need in providing a light-emitting diode with enhanced light-emitting efficiency, even without a transparent window, so as to prevent the active current from entering the bottom region of the second electrode and thus improve the light-emitting efficiency and the brightness.
Accordingly, it is the primary object of the present invention to provide a light-emitting diode with enhanced light-emitting efficiency, in which a ring-shaped groove is formed to divide an epitaxial LED structure into a first epitaxial LED region and a second epitaxial LED region, and an insulating layer is formed in the groove and on the top surface of the first epitaxial LED region, such that the active current is surely prevented from flowing through the first epitaxial LED region under the bottom layer of the second electrode, thereby enhancing the light-emitting efficiency of the LED.
It is another object of the present invention to provide a light-emitting diode with enhanced light-emitting efficiency, in which a light-reflective layer is formed in the groove and on the top surface of the first epitaxial LED region, thereby enhancing the brightness of the LED.
It is still another object of the present invention to provide a light-emitting diode with enhanced light-emitting efficiency, in which a transparent window layer is omitted according to practical use, thereby reducing the volume of the LED.
In order to achieve the foregoing objects, the present invention provides a light-emitting diode with enhanced light-emitting efficiency, comprising: a substrate; a first electrode formed on the bottom surface of said substrate; an epitaxial LED structure having a pn junction formed on the top surface of said substrate, wherein a groove is formed on said epitaxial LED structure to pass through said pn junction such that said epitaxial LED structure is divided into a first epitaxial LED region and a second epitaxial LED region, and in said groove are formed a side light-reflective layer and an insulating layer; a bottom insulating layer formed on the top surface of said first epitaxial LED region; a second electrode formed on the top surface of said bottom insulating layer; and a plurality of extending conductive contacts formed on the top surface of said second epitaxial LED region, each of said extending conductive contacts connected to said second epitaxial LED region through an extending conductive wire.
Other and further features, advantages and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings are incorporated in and constitute a part of this application and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.